© 2021 by the authors.The aim of this study is to examine the cognitive flexibility before and during the COVID-19 pandemic through a different performance measurement suitable for online application. In the study, three different data collected in 2019 (T19), 2020 (T20) and 2021 (T21) were compared with both within-and between-subject designs. One-hundred-and-twenty-three university students were included in the study for within-subjects, 239 for between-subject. According to the findings of the study, the cognitive flexibility of the students who continue formal education in T19 is higher than the students who continue distance education in T20 according to both within-subject and between-subject design. Besides, in both designs, fewer total words were produced in T19 than in T20. The sentences created by the students who continue their distance education in pandemic stay around less categories and contain more words. According to the within-subject findings obtained at T20 and T21, the cognitive flexibility and total words produced at T20 were greater. In other words, the scores of the students decreased over time during the pandemic period. In T21, cognitive flexibility is not related to vulnerability, perceived risk, and fear of COVID-19. However, according to the regression results, vulnerability at T21 was predicted by the total word and total emotional word in T20. Accordingly, producing more total words in T20 reduced vulnerability in T21; however, using more emotional words in T20 increased vulnerability in T21. In addition, the number of siblings was negatively associated with vulnerability. Lastly, cognitive flexibility test was found to be reliable.